virus

    Cards (60)

    • What are the general characteristics used to distinguish viruses?
      Size and cultivable nature
    • Why can't viruses be seen with a light microscope?
      Because they are too small
    • What is the size range of viruses?
      20 nm to 1000 nm
    • How do the small size and cultivable nature of viruses compare to some bacteria?
      They are shared with Rickettsia and Chlamydia
    • What does it mean for viruses to be obligate intracellular parasites?
      They cannot replicate outside a host cell
    • What is a distinctive feature of viruses regarding cellular structure?
      They have no cellular structure
    • What type of nucleic acid do viruses contain?
      Either RNA or DNA
    • What surrounds the viral genome?
      A protein coat called capsid
    • How do viruses multiply?
      By using the host cell's machinery
    • What is the impact of viral multiplication on drug development?
      It affects host cell function
    • What are the differences between viruses and bacteria?
      • Viruses are obligate intracellular parasites; bacteria are not.
      • Viruses lack a plasma membrane; bacteria have one.
      • Viruses do not reproduce by binary fission; bacteria do.
      • Viruses can pass through bacteriological filters; bacteria cannot.
      • Viruses may possess RNA or DNA; bacteria possess both.
      • Viruses lack ATP-generating metabolism; bacteria have it.
      • Viruses do not have ribosomes; bacteria do.
      • Viruses are sensitive to antibiotics; bacteria are also sensitive.
    • What are the two life cycle stages of every virus?
      Replicating stage and virion stage
    • What is the role of the capsid in a virus?
      It protects the viral genome
    • What are capsomeres?
      Subunits that make up the capsid
    • How are helical viruses shaped?
      They are generally rod-shaped
    • What is the shape of polyhedral viruses?
      They form equilateral triangles
    • What is the function of glycoproteins in enveloped viruses?
      They assist in host cell invasion
    • What is a complex virus?
      A virus with appendages for attachment
    • What is the significance of the viral genome's nucleic acids?
      They can be DNA or RNA
    • How do single-stranded RNA viruses differ in their strands?
      They can be + sense or - sense
    • What does the Baltimore classification system focus on?
      How viruses generate mRNA from genomes
    • What are the two classification systems for viruses?
      1. International Committee on Taxonomy of Viruses (ICTV)
      2. Baltimore classification
    • What is the highest classification level in the ICTV system?
      Order (-virales)
    • How is poliovirus classified in the ICTV system?
      Order: Picornavirales, Family: Picornaviridae
    • What is the significance of the Baltimore classification for unassigned viruses?
      It provides a method to classify them
    • What are the key features of the Baltimore classification groups?
      • Group I: dsDNA
      • Group II: ssDNA
      • Group III: dsRNA
      • Group IV: (+)ssRNA
      • Group V: (-)ssRNA
      • Group VI: (+)ssRNA-RT
      • Group VII: dsDNA-RT
    • What is the role of reverse transcriptase in some viruses?
      It synthesizes dsDNA from ssRNA
    • How do ICTV and Baltimore classifications complement each other?
      • ICTV focuses on morphology and pathology.
      • Baltimore focuses on mRNA generation.
      • Highest classification level is based on Baltimore grouping.
    • What is the genome size range of most viruses?
      2 kbp to ~2 Mbp
    • How do RNA viral genomes compare to DNA viral genomes?
      RNA viral genomes are generally smaller
    • What types of proteins do viral genomes encode?
      Structural proteins and replication proteins
    • What does the host provide for viral replication?
      Protein synthesis, tRNA, ribosomes, energy
    • What happens to the host cell during viral multiplication?
      The virus hijacks host machinery, affecting the cell
    • How many daughter virions can arise from one host cell?
      Several thousand daughter virions
    • What are the two alternative mechanisms of viral replication?
      • Lytic cycle (host cell dies)
      • Lysogenic cycle (host cell lives temporarily)
    • What are the five distinct stages of the lytic cycle?
      1. Attachment
      2. Penetration (entry)
      3. Biosynthesis
      4. Maturation
      5. Release
    • What is the first stage of the lytic cycle?
      Attachment
    • How do T-even phages attach to bacterial cells?
      Using tail fibers to bind to cell wall
    • What weakens the bacterial cell wall during penetration?
      Phage lysozyme
    • What happens to the viral DNA during penetration?
      It enters the bacterial cell through the tail core
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